This invention relates generally to media sheet feed mechanisms, and more particularly, to a media sheet pick and feed system which operates effectively regardless of media tray content and which enables easy re-loading of the media tray.
Print recording devices, such as printers, fax machines and copy machines, and print scanning devices often include an input media tray. A media sheet is picked from the input tray and fed along a media path to receive print recording or to undergo print scanning. One common mechanism for picking and feeding a media sheet employs a D-shaped wheel. During rotation of the wheel the curved portion contacts and picks a media sheet. Subsequent to the pick action the flat portion of the D-shaped wheel is adjacent to the picked media sheet, but out of contact with the media sheet. The media sheet is fed from the media tray while the flat portion of the wheel is adjacent but out of contact with the media sheet.
Another known pick mechanism includes a drive gear mounted on a shaft which in turn is coupled to a drive motor. The drive motor turns the shaft and drive gear during a pick operation. The drive gear engages a driven gear to which is rigidly connected a pick roller. Thus, the drive motor rotates the pick roller. The pick mechanism is moved into and out of contact with a media sheet to be picked by the rotation of the drive gear. When the drive gear rotates in one direction the driven gear and pick roller move into contact with a media sheet. Continued rotation in such direction causes the media sheet to be picked and moved onto a media feed path. Typically, rotation in the opposite direction causes the drive gear and pick roller to move out of contact with the media sheet. A shortcoming of this mechanism is that a spring-loaded tray is needed to bias the media sheets toward the pick range of the pick roller. Further, the media tray needs to be removed during reloading (or alternatively a mechanism is needed during reloading to depress the spring-loading plate which raises a media sheet into the pick range).
In U.S. Pat. No. 5,547,181 issued Aug. 20, 1996 to Underwood for "Media Sheet Pick and Feed System," Underwood discloses a clutch mechanism which allows the pick roller to remain in contact with the media sheet as the media sheet continues out of the media tray along the feed path. In particular, the clutch disengages the drive gear from the drive motor allowing the pick roller (along with the drive gear and driven gear) to "free" wheel. This approach eliminates the need for a spring-loaded media tray.